Collet type pulling head



Sept. 11, 1945. A. s. MULLGARDT COLLETy TYPE PULLING HEAD Filedv May l0, 1943 Patented Sept. 11, 1945 UNITED ,STATES PATENT OFFICE Alexander S. Mullgardt, Los Angeles, Calif., as-

sgnor to Cherry Rivet Company, Los Angeles, Calif., a corporation of California Application May 10, 1943, Serial No. 486,412

6 Claims.'v (Cl. 21S-.19)

This invention relates to a pulling mechanism of a riveting device commonly known as a riveting gun. This device includes a plunger or draw bolt which engages the head of the rivet and pulls the shank or inner stem of the rivet outwardly in the tubular rivet body, thereby upsetting a head on the inner end of the rivet that projects through the plates from the side on which the riveting gun is located. Usually this tool is held in the hand of a mechanic or workmanwho is using it, and is operated through the agency of a fluid-operated cylinder such as an air cylinder.

Heretofore it has been the practice to construct this arrangement, of courseI the pulling force is y not distributed over the entire area of the shoul der of the head. This of course increases the pressure per square inch on the pulling shoulder of the pulling head, which may cause a shearing of the material of the pulling head instead of having the break in the stem occur at the pointwhere it is intended to take place after the riveting movement, and after the inner head has been upset at the inner end ofthe rivet body. As usually constructed, the anvil or reaction part that holds back the rivet, also develops a relatively high concentration of pressure on a limited area, so that there is a tendency to mar the face of the rivet head. This is also objectionable.

One of the objects of this invention is to provide means for engaging the pulling head of the rivet, so constructed that the pulling pressure eX- erted upon the Vshoulder of the pulling head, will be exerted substantially throughout thevv entire area of the shoulder; also to provide a construction for the anvil that will provide an ample area of contact for it on the rivet head, which will prevent marring the rivet head.

Another object of the invention is to provide a device of this type with a colletof simple construction, presenting a plurality of jaws capable of moving apart sufliciently to enable the pulling head of the rivet to be introduced between the same and associated with other parts cooperating with the collet in such a Way that the jaws Will operate to converge on the shank of the stem adjacent its pulling headA just prior to the riveting movement, that is to say, the movement of the collet by the traction force that draws the collet away from plates that are being riveted together; alsoA tol provide. a` construction for -these parts which will enable the pulling head of the rivet to be readily inserted, and to enable the parts to be operated by the riveter so that a slight relative movement of the parts including the collet, `will converge the pulling jaws of the collet and set them closely around the stem of the rivet at the pulling head.

A further object of the invention is to provide a construction for the collet, which will enable it to be readily constructed as a one-piece collet.

Further objects ofthe invention `will appear hereinafter.

The invention consists in the novel parts and combination of parts to be described hereinafter, all of which'contribute to produce an efcient collet type pulling head.

A preferred embodiment of the invention is described in the following specification, while the broad scope of the invention is pointed out in the appended claims.

In the drawing:

Fig. l is a vertical section and partial elevation of the riveting head of a pneumatic riveting gun, and illustrating the location of the mechanism of my improvement in this device, together with the upper end of an operating lever which is usually provided in a device of this kind for operating the plunger or draw bar that pulls the rivet stem.

Fig. l2 is a longitudinal verticalsection taken in the same plane as Fig. 1, and upon an enlarged scale, but omitting the lever and contiguous parts of the machine. This view illustrates the parts involved in this invention, with their axis disposed in a horizontal plane, although in practice, the riveting head of the device is usually slightly tilted upwardly at its forward end as illustrated in Fig. 1. Fig. 2 indicates the rivet in dotted lines, and illustrates the position of the jaws of the collet in their closed position around the rivet stem, and so that they can exert their traction force upon the shoulder of the pulling head.

Fig. 3 is a view similar to Fig. 1, but showing only the forward portion of the mechanism at this point, and illustrating the collet and associated parts in their open position ready to receive the pulling head of the rivet stem.

Fig. 4 is a front elevation of a closer or enveloping device that I prefer to employ, shown in association with the collet for 'assisting the collet to perform its function of engaging the pullinghead and exerting the tractive force upon the same. 'Ihis view shows this collet `closer in its closed position.

Fig. 5 is a front elevation of the collet, and showing the same in its closed position.

Referring more particularly to the parts, I indicates the upper end or guiding head of the riveting device or gun 2and this guiding head is usually provided with a longitudinal bore 3 in which a tractor 4 in the form of a double-headed collar moves to or fro in the operation of the machine. In the device illustrated, the tractor 4 is actuated through the agency of a lever 5 having two forks 6 thatengage between'the two heads 4a and 4h ofthe tractor. f

Referring to Figs. 2 and 3, I provide a collet 'I which is attached to the tractorl by any suitable Y means to enable the tractor to pull the collet with it in the riveting movement. In the present instance, the collet is formed in one piece, the innerl end being in the form of an annular body orferrule 8 which is attached by a thread connection 9 in the interior of the head 4a. This collet is formedwith a plurality of integral lingersV I Il that have jaws I I at their iorward ends forengaging the shoulder of the rivet head I2 indicated in dotted lines. In the present instance, I employ four iingers I0 provided with their respective jaws, and the collet is preferably constructed by cutting four longitudinal slots I3 in its wall.

The construction should be such that these fingers IU are capable of separating suiciently to facilitate the introduction of the rivet head by longitudinal movement into the collet. For this purpose the forward ends of the jaws II are preferably provided with inclined faces I4. In order to effect the automatic opening of the collet when it is to receive the pulling head 'of the rivet, I prefer to construct these fingers III as spring n'gers, that is to say, the entire collet is formed of material having sunicient resiliency to accomplish this; in other words, the ngers IIJ are spring fingers, and naturally tend to assume a positionin which the jaws II are held apart. In the operation of the device,v it isconstructed so that when the pulling head I2 has been inserted in the open end of the collet, then the next` movement by the operator will effect the converging of the jaws onto the rivet stern adjacent its pull- `ing head. In order to accomplish this, I prefer to provide the end of the guide head I with an annulus I5 which is attached in the end of the guide head by a thread connection I6 substantially as shown. When the tractor 4 is moved rearwardly by the actuating lever 5 in the riveting movement, the fingers IEl are pulled through this annulus in their converged relation.

In order to facilitate this mode of operation, I prefer to provide a collet closer and guide I1 which is preferably composed of a plurality of sections that abut together at their side faces so as. to operate when closed, as though it had a solid continuous circumferential wall. This collet closer may also function as the anvil to take the reactive thrust. of the outer rivet head when upsetting fthe rivet sleeve, and hence inthe present instance, I have illustrated the closer as-composed of three separatedfsections I'Io, I'Ib, and I'Ic, each occupying 120 of the circumference around the collet. Each of the sections I'Ia, IIb, I'Ic, is enlarged at its forward end so as to present a shoulder ISI that can seat against the end ofthe annulus I5 in a closed position of the closer and collet., but. in the open position is disposed slightly away iro-m this face. lAfter the pulling head I2 has been inserted in the collet, then 'they riveter moves the closer inwardly ortoward the right as viewed in Fig. 3, and this movement is a relative movement with respect to the collet.

Correleated means is provided whereby this movement collapses the closer II, and its collapsing also collapses the collet, causing the jaws II to converge on the pullingstem of the rivet.

In order to accomplish this, I prefer to provide each jaw or section Ila, IIb, I'Ic, of the closer, with an inclined shoulder 20, and this shoulder cooperates with an annular inclined shoulder 2| at the forward face of the annulus. Each of the sections of the closer I 'I has an elongated body or shank 22 extending longitudinally Within the bore of the annulus, and each of these Shanks bears on its outer face against an annular bearing face 23 formed at the inner end of the annulus. Beyond the inner face of the annulus the Shanks 22 project, and are rather loosely connected together by means of a spring ring 24 seating in notches 25 formed respectively in the shanks 22.

The projecting ends of these Shanks 22 are short enough to permit the slight relative longitudinal movement that is necessary to enable the sections of the closer I'I to move from their open position shown in Fig. 3, to their closed position shown in Fig. 2.

A In order to prevent any possibility of the constant opening'and closing movement of the iingers, tending to strain the metal at the inner ends of the slots I3, I prefer to provide radially drilled holes 26 at these points, with which the inner ends of the slots communicate. This of course prevents the slots from forming an angle or corner in the collet, which might tend to start a crack.

If desired, the inner end of the annulus I5 may be provided with a counterbore to form an iny clined shoulder 2T that operates as a seat for the spring ring 24 to limit the forward movement ofv the closer II, as illustrated in Fig. 3.

In the operationv of the device, it will be evident that the inner faces of the shanks 22 cooperate to guide the fingers 'I and maintain them in their closed position during the riveting movement. In order to enable them to perform this function more eil'ectively, the Shanks 22 have concave inner faces 28.

When the riveting operation commences, of

' course the outer head 29 of the rivet body is seated on the face of the outer plate of the plates that are to be riveted together, and as soon as the pull commences, the riveting head of the device is pulled in toward the plates so that the Hat boss or nose 3D of the closer I1, seats against the outer face of the rivet head 29, and operates as a back-stop to hold the rivet firmly in place thereafter and while the traction force is being exerted upon the pulling stem 3| of therivet. At this time of course, the shoulders I9 of the segments of the closer are seated solidly up against the forward endof the annulus.

By reason of the fact that the sections of the anvil and collet closer I'l t closely against each other at its nose 30, in the closed position of the anvil shown in Fig. 2, the entire area of the rivet head is subjected to the same pressure so there is no possibility of forming any projections or marred points on the rivet head.

Many other embodiments of the invention may be resorted to without departing from the spirit of the invention.

What I claim is:

1. In a pulling mechanism for exerting traction upon the pulling head of a rivet, the combination of a power-actuated tractor, guide means for guiding said tractor in the riveting movement, a collet connected to -said tractor and having a plurality of separable ,iaws capable of passing over the said pulling head and converging thereafter to engage the shoulder of the pulling head, a collet closer and guide having limited relative longitudinal movement with respect to the collet for effecting the closing of the collet by a movement of the collet closer in a rearward direction at the starting of the riveting movement, thereby converging the jaws of the collet to engage the shoulder of the pulling head substantially all around its circumferential area, and operating during the riveting movement to maintain the jaws of the collet in their closed position.

2. In a pulling mechanism for exerting traction upon the pulling head of a rivet, the combination of a power-actuated tractor, a collet connected to said tractor and having a plurality of jaws at its forward end constructed so that they are urged to separate from each other when the collet is disposed in an extreme forward position, thus enabling the rivet head to be moved into the forward end of the collet to be engaged by the said jaws, an annulus coaxial with the axis of the collet, with a bore therein, said tractor and annulus cooperating to converge the said jaws when the collet is moved rearwardly within the annulus at the start of the riveting movement, the said jaws operating to engage the shoulder of the pulling head at circumferentially spaced points about the same.

3. In a pulling mechanism for exerting traction upon the pulling head of a rivet, the combination of a power-actuated tractor, guide means for guiding said tractor in the riveting movement, a collet connected to said tractor and having a, plurality of circumferentially spaced yielding expanding fingers extending longitudinally of the axis of the collet and having jaws respectively at their ends for engaging the shoulder of the pulling head, a collet closer enveloping the said fingers and composed of a plurality of separable sections coaxial with the collet and each having an inclined shoulder, said closer being capable of limited longitudinal movement relative to the collet; and relatively xed means cooperating with said inclined shoulders when the collet closer is moved rearwardly relative to the said collet to converge the jaws of the collet to engage the shoulder of the said pulling head, the inner faces of said sections of the collet closer cooperating to guide the said jaws and maintain the same in their close position during the riveting movement.

4. In a pulling mechanism for exerting traction upon the pulling head of a rivet, the combination of a power-actuated tractor, guide means for guiding said tractor in the riveting movement, a collet connected to said tractor and having a plurality of circumferentially spaced spring n gers extending longitudinally of the axis of the collet and capable of assuming an expanded position due to their own resiliency, said expanding fingers having jaws respectively at their ends for engaging the shoulder of the pulling head, a collet closer enveloping the said ngers and composed of a plurality of separable sections coaxial with the collet and each having an inclined shoulder on its outer face, said guide means having an annulus surrounding the said collet closer with an inclined shoulder adjacent the inclined shoulders on said sections, said closer being capable of limited longitudinal movement relative to the collet, said inclined shoulders and the inclined shoulder of the annulus cooperating when the closer is given a relative inward movement with respect to the collet, to converge the said sections and thereby converge the said jaws to engage the shoulder of said pulling head, said closer sections having concave inner faces cooperating to guide the collet jaws in the riveting movement and maintain the same in their closed position.

5. A pulling mechanism constructed as defined in claim 1, in which the collet closer is formed with a nose to seat against the head of the rivet body to operate as an anvil for the same when the stem of the rivet is being pulled in the riveting movement.

6. A pulling mechanism for rivets equipped with pulling heads, comprising: a tubular holder, a multiple-jaw collet reciprocable in said holder and adapted to fit over and engage the pulling head of a rivet, a multiple-jaw collet-constrictor reciprocable in said holder and surrounding said collet, said constrictor including radially movable anvil segments adapted when in their radially inner position to bear against said rivet, means for reciprocating said collet, and means incorporating said constrictor and said holder to move said anvil segments radially inward thereby to constrict said collet.

ALEXANDER S. MUILLGARDT. 

